Answer this question truthfully
### Question: What causes Sickle-cell disease?
### Response: Sickle cell anemia is caused by an abnormal type of hemoglobin called hemoglobin S.
Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S changes the shape of red blood cells, especially when the cells are exposed to low oxygen levels. The red blood cells become shaped like crescents or sickles. The fragile, sickle-shaped cells deliver less oxygen to the body's tissues. They can also get stuck more easily in small blood vessels, and break into pieces that interupt healthy blood flow.
Sickle cell anemia is inherited from both parents. If you inherit the hemoglobin S gene from one parent and normal hemoglobin (A) from your other parent, you will have sickle cell trait. People with sickle cell trait do not have the symptoms of sickle cell anemia. In order to get sickle cell disease, both of your parents must have at least 1 defective gene. If both of your parents have sickle cell trait, then there is a 25% chance that you will get sickle cell disease.